The Space Shuttle Approach and Landing Tests

The space shuttle orbiter was the first spacecraft designed with the aerodynamic characteristics and in-atmosphere handling qualities of a conventional airplane. In order to evaluate the orbiter’s aerodynamic flight control systems and subsonic handling characteristics, NASA Dryden Flight Research Center undertook a series of flight tests, known as the Approach and Landing Test program, at Edwards Air Force Base, Calif., in 1977.

A full-scale orbiter prototype, named Enterprise, was built for the program. Because the vehicle would not be subjected to re-entry heating, Enterprise had no need for a thermal protection system. It was not covered with the space shuttle’s reusable surface insulation, but with substitute materials, primarily polyurethane foam and fiberglass. The flight deck had two crew stations for the commander and pilot.

Aerodynamic controls included a body flap at the aft end, elevons and a split rudder that doubled as a speed brake. Reaction control systems, unnecessary at low altitude, were not installed. For the captive flights and the first three free flights, an aerodynamic fairing covered the orbiter’s aft end. Three dummy main engines were installed for the final two flights to simulate weight and aerodynamic characteristics of an operational orbiter.

Space shuttle prototype Enterprise rises from NASA's 747 Shuttle Carrier Aircraft.Without the aerodynamic tailcone over its dummy engine nozzles, the space shuttle prototype Enterprise rises from NASA's 747 Shuttle Carrier Aircraft to begin a powerless glide on its fourth of the five free flights in the Approach and Landing Tests on Oct. 12, 1977.

The Enterprise was to be carried aloft by, and eventually released for flight from, a modified Boeing 747. This Shuttle Carrier Aircraft or SCA, as it came to be known, had a fuselage strengthened at key stress points, two vertical fins attached to the horizontal stabilizers, and three attach points on top of the fuselage to anchor the orbiter. All original seating and interior trim except that of the first class section of the main deck was removed to reduce weight.

Wind-tunnel-model tests allayed concerns over the separation characteristics of the two vehicles in flight. Because of the orbiter’s positive angle of attack while mated to the 747, the Enterprise tended to lift or climb relative to the SCA. Meanwhile, the 747 began to descend as the crew idled the engines and deployed lift spoilers, allowing the orbiter to clear the SCA’s tail in about 1.5 seconds.